Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$176.45	12.312%	$198.1745	$198.17	$198.15	$198.20
Purchase #2	$41.74	8.139%	$45.1372	$45.14	$45.15	$45.10
Purchase #3	$156.39	7.707%	$168.443	$168.44	$168.45	$168.40
Purchase #4	$112.60	9.831%	$123.6697	$123.67	$123.65	$123.70
Purchase #5	$203.55	5.589%	$214.9264	$214.93	$214.95	$214.90
Purchase #6	$28.93	12.596%	$32.574	$32.57	$32.55	$32.60
Purchase #7	$72.64	7.444%	$78.0473	$78.05	$78.05	$78.00
7 purchase totals =	$792.30		$860.9721	$860.97	$860.95	$860.90